Crawler tumbler and track shoe



Sept 3@, $58 H. v. BANNISTER CRAWLER TUMBLER AND TRACK SHOE 3Sheets-See; 1'

Filed Feb. 2, 1955 Sept. 3@, 198 H. v. BANNISTER 2,854,294

CRAWLER TUMBLER AND TRACK SHOE Filed Feb. 2, 1955 3 Sheets-Sheet 2jive/7 for; Harold V. Bcnnisier 37 53, M L/v 777m A TY Sept. 3%, 1958Filed Feb. 2, 1955 H. V. BANNISTER CRAWLER TUMBLER AND TRACK SHOE 5Sheets-Sheet 3 Harold V. @unnisier United States Patent CRAWLER TUMBLERAND TRACK SHOE Harold V. Bannister, Waverly, Iowa, assignor to Schield3antam Company, Waverly, Iowa, a corporation of owa Application February2, 1955, Serial No. 485,797

21 Claims. (Cl. 305-) This invention relates to improvements in finaldrive assemblies for endless track mechanisms and more particularly toimprovements in the construction of the driving sprocket or tumbler forendless tracks and in the construction of an endless track associatedtherewith.

In present constructions, endless tracks are formed from a plurality ofpivotally connected or linked track shoes or pads, each of which has anupstanding lug thereon for engagement by a driving sprocket or tumbler.The lugs are usually of rectangular configuration and the drivingsprocket or tumbler associated therewith simultaneously engages severalof these lugs for movement of the vehicle along the endless track.Although this conventional method of drive is entirely satisfactoryunder most conditions, the action between the tumbler and the lugs onthe track pads is largely one of sliding engagement. Necessarily,therefore, a high quality of materials must be used. However, under someconditions such as in sandy soil or where the soil is highly abrasive,very rapid wear is encountered. So much so, in fact, that in some casesan endless track as well as the drive tumblers may be entirely worn outand may require complete replacement within a period of two or threeweeks. This, of course, is an expensive proposition and presents a veryreal problem in the art.

It is, therefore, one of the aims of this invention to provide animproved drive for endless track vehicles which will reduce wear betweenthe drive sprockets and tumblers and the track pad lugs.

Another object of this invention is to provide an improved drive forendless track vehicles wherein rolling contact is efiected between thetumblers and the track pad lugs, to minimize friction and wear.

Another object of this invention lies in an improved drive in accordancewith the preceding object wherein the drive is equally capable ofsatisfactory operation in both forward and reverse directions.

Another object of this invention is to provide an improved drivesprocket or tumbler construction which utilizes roller means as thedrive elements and which is so constructed that the rollers may beeasily interchanged or replaced to compensate for wear while at the sametime the construction does not detract from the rigidity and strength ofthe sprocket.

Another object of this invention is to provide an involute form of trackpad lug and a drive sprocket associated therewith having roller drivemeans thereon whereby frictionand wear-reducing characteristics areimparted to the assembly.

Still another object of this invention resides in the provision of animproved endless track and drive sprocket association wherein the pitchof the sprocket drive elements is greater than the pitch of the trackpads engaged volute construction of a track pad lug and driveintroductory ramp portions associated therewith.

Still another object of this invention lies in the pro vision of animproved form of endless track and drive sprocket therefor wherein thepitch between the drive rollers of the sprocket is greater than thepitch between adjacent track pad lugs engaged therewith and in theconstruction of the track pad lugs wherein they are of involuteconfiguration and have drive introductory ramp portions associatedtherewith to effect a rolling contact with the rollers and guide thesame therealong for smooth and shockless drive introduction with theinvolute lugs.

Another object of this invention is to provide an improved form of finaldrive for endless tracks in which a tumbler or sprocket incorporatescircumferentially spaced pin members whereas the track shoes embodyupstanding involute form lugs and drive introductory ramps mergingsmoothly therewith so that the centers of pivotal connection betweenlugs revolve at a constant radius from the center of the sprocket whileportions of the shoes are permitted of radial shifting with respect tothe sprocket or tumbler.

A further object of the invention lies in the provision of a final driveassembly for endless track vehicles in accordance with the precedingobject, wherein the tumbler or sprocket incorporates a pair of spacedbut rigidly interconnected wheel plates and mounting pins associatedtherewith upon which replaceable roller means are mounted.

A further object of the invention lies in the provision of a final driveassembly for endless track vehicles in.

accordance with the preceding object, wherein the tumbler or sprocketincorporates a pair of spaced but rigidly interconnected wheel platesand mounting pins associated therewith upon which replaceable rollermeans are mounted, the roller means being of selectively largerdiameters whereby to compensate for wear of the track lugs and driveintroductory ramps as well as to compensate for wear occurring in thehinge joints between track lugs.

Another object of this invention resides in the provision of an improvedfinal drive in accordance with the preceding object wherein portions ofsaid wheel plates on opposite sides of said pins serve to absorb andcompensate for side thrust and prevent lateral shifting of associatedendless track elements.

These, together with other objects inherent in the construction andfunctioning of the apparatus will appear as this description proceeds.

Illustrative embodiments of the invention are shown in the accompanyingdrawings but it is to be understood that this showing is illustrativeonly, and is not intended to be limiting to the exact constructionshown, since obviously changes can be made both in detailed constructionand arrangement of parts without forming a departure from the spirit andscope of this invention as set forth and defined in the appended claims.

In the drawings:

Fig. 1 is an elevational view partly broken away, showing a portion ofan endless track constructed in accordance with this invention andshowing the drive sprocket associated therewith;

Fig. 2 is a vertical transverse section taken generally along the planeof section line 2-2 in Fig. 1;

Fig. .3 is a perspective view of one of the track pads constructed inaccordance with this invention;

Fig. 4 is an elevational view showing one endless track assembly and itsassociated supporting and driving mechanisms in their entirety;

Fig. 5 is an enlarged elevation showing a portion of the drive sprocketand endless track and illustrating the relationship therebetween;

Fig. 6 is a side elevational view of a modified form of drive sprocket;and

by .any suitable means suchas welding .or the like, and

which projects on opposite .sides "thereofin the-manner shownmostclearlyinFig. 2. The hub is provided with .a;longitudinal.bore and.a:keyway 16 intersecting the bore..whereby to receive a driveaxle of.the associated ehicle as indicated by the reference character 17 in.ig. 4. I

The contour or marginal edge of the wheel plates em bodiesa series ofvalleys 18 interconnected by :radially projecting guide or thrustportions 19. Each guideportion 19 presents a flat chordal edge20 andarcuatecorner ,porti0ns21 and 22. Theguide portions 19 are additionallyeach provided with a pair of apertures 23 and 24 adjacent the respectivecorners 21 and 22.

It will benoted that the two wheel plates are secured together instaggered relationship such that the valleys .18 of .onewheel plate aredisposedbetween twozadjacent valleys 18 of the other wheel plate andsuchtthat-the guideportions 19:of one plate .are .in bridging relation.to the valleysof the other plate. .The apertures :23 "and 24 are spacedatequal circumferential distances around the periphery of the driveplates and eachregistering pair of these apertures is adapted to receivea pin member .25 therethrough. As seen most clearly in Fi-g...2, for thepurpose of retaining the pins 25 properly t in place alock collar or.sleeve 28 .is engaged :over the end .27 ,of each pin and a lock pin 29is projected through .the lock collar andtheend 27 of thepin to hold.thecollar or sleeve in place in the manner shown. In this respect, itwill be noted that the end 27 of the .PlHfPI'QjCCtS .outwardlyof theinnerwheel plate12 so that the lock collar .28 is .engaged.againsttheinner .side of the inner wheel .p1ate.12.

Rotatably carried by each of the pins :is a cylindrical roller member 30which rollers .form the drive-elements ,of thetumbler assembly as willbe more readily apparent as this description proceeds.

The felloe portion of the wheel plates Hand 12 -are provided withapertures 31 and it will be noted that these apertures are equal innumber to the guide portions 19 and project partially into such guideportions. .T he openings 31 serve not only for the purpose of lighteningthe wheel plates. but also serve to 2 permit dirt clods, rocks and otherforeign material to be expelled from the drive tumbler assembly.

i the iarcuate ;p.ortion 45,'is also arcuate.

The specific contour of the wheel plates 11 and 12,"

that is, the formation of the alternate valleys .and guide portions,serves also to lighten the construction .whereas the-staggeredrelationship between the valleys of the inner and outer wheel plates;assures that the'maximumamount of material may be removed from thevalleys; Thatyis, more material can be removed. from each valley-1.8 bystaggering the relationship of thevalleys between the @two wheel platesthan would be possible suchvalleys were in transverse registry.

.It will benoted that the staggered relationship ,of .the .guide orthrust portions .19 does .notdetract fromythe lateral thrust stabilitywhich theyaccomplish; The -here- :inaftendescribed track shoe lugs socooperate with :the drive or thrust portions that every other track:shoe :is prevented from shifting laterally by the .guiderportions'onzone; side of the sprocket while;the,; intermediate alternate shoesbear against the other guidennthrust'portions 19 to prevent lateralshifting of the shoes in the opposite direction.

The construction of each of the track pad members 32 will be mostreadily apparent from Figs. 1 and 3. The track pads are'conventionalinsofar as each includes a main body portion 33 having aground-engagingsurface 34 on one side thereof, and having at opposite ends lug portionsv 3.5, .36 and 37 whichareapertured .fortthe reception ofinterconnecting pin members 38 by meansof which'the plurality 'of trackpads :are linked *or pivotdlly interconnected for--cooperation in the'well known manner. The surface 39 of the main body portion 33 which isoppositeito.thegroundiengaging surface .34;is provided with anupstanding lug. indicated generally by the reference character 40which'is'also conventionally provided although the specificconfiguration of the lug departs from that which is normally utilized.In this respect, it will be rooted that each .lug -40 :includes a.relatively ;wide

.base portion 41 joined with and extending; longitudinally of the main.body portion -33,the base tapering or:.b,eing involutely formed in.such-.a-manner that it: presents :;a relatively ,narrow upper .orfreeends-portion 142. The roller engaging face- .43 .of each'lug is ofinvolute :configuration.

:Adjacent the drive face of each, lug :.and,formed1integrallytherewith-and with ,the ;main body portion 33 .-a :drive introductoryramp 44. This drive introductory ramp,extends-;from a;point adjacent oneend 10f theztrack gpaddn. a direction toward the jdrive face 43 .1.and;merges smoothly-therewithvin :an :arcuate face portion 45. .fI'hefreeendof lthe ramp-46 is -,the.1highest point .thereofzand the surface471 ofethe ramp in thisivicinitynnergingioward Therelationship of the:surface 47 ofthe;ramp with the arcuatersurface .45 and therelationshipof the involute drive ;face:43 cof the log with the ramp-surface.45.--is.tangentialxsuchzthat smooth and 1 shockless: rolling. contact'can behadbetween the tumbler -.ro1lers :30 as these members .roll along:the

drive introductory-surface into: contact with ctheinvohte. drive surfaceof the lugs. -As=will ,bezseemmostcclearly :from Fig. -5,;the radius-rof the ramp surface .45 is :equal to the radii of the drive rollermembers whereas the. radius ,R of-the ramp :surface .47, is .equal tothe radiussofanzarc tangent torall of :the drive .rollers. Thus, as:thefrlrivc :rollers; progressively roll along .the ramp surfaceA'l, thecenters of the hinge pins 38. remain at; afixe'd .eandconsttint.distance,fromdtheacenter ofv rotation of thed'rivenprocket. Atfthesame-time, when any onevdrive roller'reachcsrathe point at which itengages the ramps-surface 45, thatrroller will impart the drivetothetrack and-will do ,so inia very efficient manner inasmuchas amaximum-portion .of the roller zsurface equal in lengt-htothelengtht-ofathe ramp surface 45 'wilLbe engaged.

Of prime consideration with respectto the properpop- .eration of thisinvention. is the. fact that the; circumferential pitch between therotational centers of the;roller members 30 is greater than .thecircumferential pitchi between adjacent track pad lugsas the padsare'engaged upon the tumbler assembly. This relationship of pitchesassures that the-interen gagement ,bet-weenthe successive drive rollers30 and the correspondingutrack pad,lugs.is had .in the mannerillustrated in z-Eig. l. ';That;is,.'the roller 48 in Big, 1 awhichvhas, justengaged-withzthegramp portion of the-track pad 49in thatfignreengages-upon the end ramp ,surface 47 .outsoficontact with theinvolute drive surface of the associated lug=;40 whereas; the. driveroller which isin'dicated bylthe reference ,charactcr SO in 'Fig. Land.whichris removed asubstantial circumferential distance, from .thepreviously mentioned roller 48.11215 justengaged with :the lowermost,portion-of-the involute face ofits associated lug 40. "From theposition. -of .the roller 48 with relation to itscorrespondinglugtdrivegsur face 43, the intermediate -rollers.which; are,designatediby the reference characters 51, .52 and.-53,ware,"progressively closer to their associated involute lug ,drive;surfacesuifi,

this being effected by the differential in pitch previously discussed.Thus, as the tumbler assembly is rotated in a counter clockwisedirection in Fig. l, the roller 48 will progress from its position shownon the drive introductory ramp surface 47 along this surface intocontact with the arcuate surface 45 at approximately the point that theroller53 is disposed and will, when the roller 48 has attained theposition of the roller 50, engage the lowermost portion of the involutedrive face 43 of its associated lug. The relationship between the roller54 and its vassociated lug in Fig. l is such that these members arecompletely out of contact, this being due to the fact that theassociated track pad and lug member is not as closely engaged with thesprocket assembly due to the upward inclination of this pad by virtue ofthe positioning of the idler pulley member 55 as seen in Fig. 4. Ofcourse, even if the idler pulley 55 is so positioned that the lugassembly associated with the roller 54 rests upon such roller, therewill be no drive transmitted between the roller 54 and this lug sincethe upper flight of the endless track assembly will not be undersufiicient tension to assure this drive.

It will be understood that one important effect of the single driveengagement between the tumbler and the track assembly is that there canbe no localized overstressing of parts, such as is inherent inconventional drive ,drive elements and the lugs, the presence of foreignmaterial between any one driving element and its associatedlug will tendto place an undue strain upon an adjacent drive element and theinterposed lug and associated track pads since the foreign material willact as a wedge which cannot be compensated for since several track padlugs are drivingly engaged at the same time. In the present device, suchpresence of foreign material will only shift the relative positioning ofall the rollers and their associated lugs, that is, compensation can behad for the presence of such foreign material without placing anyfurther strain on the tumbler or endless track. It is also important tonote that not only do the drive rollers reduce friction and wear byvirtue of their rolling engagement with the track lugs, but also theypresent a far greater area of wearing surface than is ordinarily used indrive tumblers. Their rolling action assures even wearing throughouttheir circumferential surfaces. In this respect, it is desirable thatthe dimensions of the drive rollers and track lug surfaces be such thatan infinite number of driving engagements between the rollers and lugswill be required before the same surface portion of any roller will betwice in precisely the same drive engagement with the lug surfaces 45.

A further important consideration in respect to this invention will beseen to exist as a result that the effective pitch differential betweenthe drive rollers and the track pad lugs can be maintained substantiallyconstant even though wear does occur on both the rollers and the lugs bymerely replacing, as the lugs and rollers become worn, the worn rollersWith rollers of larger diameter than were initially used. Further,should any rollers become damaged unduly during use, they are rapidlyand easily replaced.

Another important consideration with regard to this invention is thatthe track shoes rotate around the tumbler about a fixed radius, thusassuring uniform tension in the chain of linked track shoes. This is, ofcourse, due to the fact that the ramp surfaces 47 always lie along anare which is tangent to all of the drive rollers, as shown most clearlyin Fig. 5.

' ing pins.

It will be noted from Fig. 5 that the leading side 56 of each track lugis of involute configuration and that at the base of each lug is anarcuate surface 57 Whose radius r is equal to the radii of the driverollers. Thus, the surfaces 45 and 57 are similar but are disposedoppositely to each other. The purpose of forming the track lugs withforward involute surfaces is to permit the track to be driven in thereverse direction. It will be noted that in Fig. 5, the full lineposition of the rollers illustrates the positioning of the drive rollerswhen the same are reversely driving while the dotted lines illustratethe forward drive position of the rollers.

Preferably, the leading sides of the track lugs are not provided withsurfaces corresponding to the drive introductory surfaces 47 on theopposite sides since the introductory surface 47 of each adjacent trackshoe will serve this purpose. This reduces to a minimum the amount oflost motion permitted of the drive tumbler between forward and reversedrive.

Referring now more particularly to Figs. 6 and 7, wherein a modifiedform of tumbler is shown, the tumbler or sprocket will be seen to beformed as an integral unit, preferably a casting, and includes a centralhub 58 and a plurality of generally radial spoke plates 59, eachprovided with a triangular opening 60. All of the spoke plates arejoined to the hub substantially midway between the ends of the latterand from this point the plates are angulated longitudinally of the hubalternately in opposite directions so that every other plate terminatesadjacent one end of the hub while the other plates terminate adjacentthe opposite end of the hub. The spoke plates are generally triangularin configuration and are apically joined to the hub so that their baseportions 61 are remote from the hub. A series of longitudinallyextending and circumferentially spaced radial webs 62 are positioned onthe hub so as to integrally connect adjacent plates along their sideedges. This particular construction serves to present a very rigid drivemember which at the same time offers practically no depressions orpockets within which dirt and the like may lodge temporarily to be laterdeposited on the track lugs and drive rollers.

The base portions 61 terminate at opposite ends in apertured bossesadapted to receive the drive roller mount- The bosses 63 in the platesadjacent one end of the hub 58 are merely thickened whereas the bosses64 on the other plates are both thickened and provided with transverseslots 65. When the drive roller mounting pins are mounted in the platebosses, the apertured ends of the pins are aligned with the slots 65whereby a lock pin may be inserted therein.

It is preferred that the hub 58 be provided with a longitudinallyextending rib 66 to maintain a substantially uniform thickness of metalin the vicinity of the keyway 67.

I claim:

1. A track shoe or pad comprising, a main body portion having aground-engaging face on one side thereof, an upstanding lug formed onthe opposite face of said main body portion, said lug being of involuteconfiguration, a drive introductory ramp formed on said opposite face ofthe main body portion extending longitudinally therealong and mergingwith the base of said involute lug.

2. A track shoe or pad comprising, a main body portion having aground-engaging face on one side thereof, an upstanding lug formed onthe opposite face of said main body portion, said lug having a driveface on one 'side thereof adjacent one end of the main body portion,said drive face being of involute configuration, a drive introductoryramp formed on said opposite face of the main body portion extendingfrom adjacent said one end of the main body portion to the drive face ofthe lug and merging smoothly with the latter.

lug. 1

4. A track shoe or ,pad comprising, a main body portionhaving aground-engaging face onone side thereof, an upstanding lug formed on-theopposite "face of said main body portion, said'lug having a drive faceon one .side thereofadjacentgoneendof the main body portion, said driveface being of jinvolute configuration, a drive introductory. ramp formedon said opposite face of the main body portion extending from adjacentsaid one end of the main body portion to the drive face of the .lug andmerging smoothly with the latter, saidrampbeing arcuated fromadjacentthe one end of :the main *body portion to merge smoothly andtangentially with the arcuate base portion of said involute drive face.

'5. In a drive assembly for endless track vehicles, a drive sprocket,said drive sprocket having a plurality of circumfe'rentially spaceddrive elements, an endless, flexible tread trained about a portion ofthe circumference of said drive sprocket, said endless tread including aplurality of pivotally linked track pads, each tra'ckpad 'having'anupstanding lug thereon engageable by the .drive elements of ,thesprocket, the pitch between the drive elements on the sprocket beinggreater than 'the pitch between the track pad lugs engaged upon thedrive sprocket, whereby driving engagement between the sprocket andthetread is had substantially only'between one drive element and one lug atany one given point ofrotation of the drive sprocket.

6.'The drive assembly according'to claim "5 wherein said lugs are ofinvolute configuration.

'7. The drive assembly according to claim '5 wherein said lugs are ofinvolute configuration, said drive-elements being of cylindricalconfiguration;

8. A track shoe or pad comprising a main bodypor- ,tion'havingaground-.engaging'lower surface, a d'riveLlug formed on the upper"surface of said main body portion, .said lug'having onesurfacethereofformed of involute configuration.

9.In a drive assembly for endless track vehicles, a "drive sprocket, aplurality of circumferentially spaced rollers journaled onsaid sprocket,a plurality of pivotally interconnected track pads trained about aportion of said sprocket, each of said track pads having an upstandinglug formed on one surface thereof engageable by's aid rollers, each ofsaid lugs being of involute configuration on at least one surfacethereof.

10. A track shoe or pad comprising a maintbody portion having aground-engaging lower surface, adrive lug projecting from the uppersurface of said ,mainihody portion, said lug having opposite drivesurfaces facing the opposite *endsof said main-body portion,-eachdrive:surfacebeing of involute configuration, and a driveintro- "ductoryramp :extendingirom adjacent one .end of .the main body; portionto;mergersmoothiy:with the baseqof .one involute drive surface.

glil. In adrive assembly for endless track vehicles, a drive rsprocket,a plurality of circumferentially spaced rollersjjournaledonsaid-sprocket, a plurality of pivotally interconnected track padstrained about a portion of-said sprocket, each of said track pads havingan upstanding luggformed on one surfacethereof engageable by saidrollers, each oftsaidllugs being of involute configuration ,on atleastone surface thereof, and an arcuate drive introductory ramp extendingf-romadjacent one end of each track'pad to mergesmoothly with the baseof the involute surface of the associated lug.

I ,12..'In'a drive assembly 7 drive sprocket, ,a' plurality of,circurnferentially. "spaced,

' or endless track vehicles, ;a

rollers journaled on said sprocket, -a pluralityof pivotallyinterconnected.trackpads trained about apor'tion of -said sprocket,eachgofsaid track pads havingan upstanding lug formed on one surfacethereof engagableby said rollers, each of said flugs being of'involuteconfiguration on at least one surface thereof, the pitch between saidsprocketrollers being greater than the pitch between the track pad lugs,whereby driving engagement between the sprocket and the endless track ishadsubstantially only between one roller and onelug at any one.givenpoint of rotation of the drive sprocket.

uration on at least one surface thereof, and pan; arcuate driveintroductory ramp extending fromadjacentnneend of each'trac'k pad'tomerge srnoothlywith the 'base of-the involute surface oftheassociated'lug, 'the pitch-between said sprocket rollersbe'ing, greaterthan the pitch betweenv the 'track pad lugs, whereby driving engagementihetween the sprocket. and the endless track is bad substantially onlybetween one roller and one lug at ,anylone given pointof rotation'ofthedrive-sprocket.

'14. In "a drive assembly for endless track-vehiclesya gdrive sprocket,said drive sprocket havingap1urality'of circumferentially spacedcylindrical drive "elementsgan endless flexible tread trained about aportion 'ofpsaid sprocket, said endlesstread including aplurality ofpivot- ,ally linkedtrackpads, each track pad having an'upstandinglugthereonengageable 'by the drive elements ofthe sprocket, :eachlughaving aninvolute drive-surface'jthe pitch between drive elements of thesprocket being greater 'than'the pitch between-the trackpadlugs,-wherebydriving engagement between the sprocket and-treadis hadsubstantially only'betweengone drive element and one-lug at any giventime.

1'5.'In a drive assemblyffor endless track vehicles, a drive sprocket,said drive sprocket having apluraIityof circumferentially spacedcylindrical ;drive elements, an endlessfiexible tread gtrained about 'aportion "of said sprockehsaid endless 'treadincludinga plurality of'pivotally linked' tr-ack pads, 'each track pad having an upstanding-lug thereon :engageable by the drive elements 'ofthe sprocket, each lughaving an involute drive surface, the pitch between drive elements ofthe 'sprocket being 'greater than the pitch between the track pad lugs,wherebydriving engagement between the sprocket and ,tread is hadsubstantially only between one drive-elementandone lug at any giventime, the base of said involute-drive surface having an arcuatesurface'fonned thereon whose radius is equal to the radii ofsaid driveelements. I

,16. In a drive assemblyfor endless "track vehicles, 'a drive sprocket,said drive sprocket having a plurality of circumferentially spacedcylindrical jdrive elements, an endless flexible tread ;.trained about aportion of ,said sprocket, said endless tread including ,a plurality ofpivotally linked track pads, each track pad, havingan upstandinglugthereon engageable by the drive elementsof the sprocket, each lug havingan involute drive sur'face,'the

pitch between drive elements of the sprocket being greater than thepitch between the track pad'lugs, .whereby fdriving engagement betweenthe sprocket an'd tread jishad substantially only between one driveelement and ,onelug at anygiven time, the base of said involute drivesurface having an arcuate surface formed thereonwhose radius is equaltothe radii of said 'drive elements, and an arcuate drive introductoryramp .on each pad merging smoothly with said arcuate surface.

17. In a drive assembly for endlesstrack vehicles a drive sprocket, aplurality of circumferentially spaced rollers journaled on saidsprocket, a plurality of pivotally interconnected track pads trainedabout a portion of said sprocket, each of said track pads having anupstanding lug engageable by said rollers, each lug presenting a pair ofinvolute drive surfaces facing opposite ends of said pads.

18. In a drive assembly for endless track vehicles, a drive sprocket, aplurality of circumferentially spaced rollers journaled on saidsprocket, a plurality of pivotally interconnected track pads trainedabout a portion of said sprocket, each of said track pads having anupstanding lug engageable by said rollers, each lug presenting a pair ofinvolute drive surfaces facing opposite ends of said pads, the base ofsaid involute drive surface having an arcuate surface formed thereonwhose radius is equal to the radii of said drive elements.

19. In a drive assembly for endless track vehicles, a drive sprocket, aplurality of circumferentially spaced rollers journaled on saidsprocket, a plurality of pivotally interconnected track pads trainedabout a portion of said sprocket, each of said track pads having anupstanding lug engageable by said rollers, each lug presenting a pair ofinvolute drive surfaces facing opposite ends of said pads, the base ofsaid involute drive surface having an arcuate surface formed thereonWhose radius is equal to the radii of said drive elements, and anarcuate drive introductory ramp on each pad merging smoothly with saidarcuate surface.

20. In a drive assembly for endless track vehicles, a drive sprocket,said drive sprocket having a centrally disposed hub, a plurality ofdrive rollers arranged in circumferentially spaced relation around saidhub with the axes of said rollers parallel z 7 the axis of said hub, aplurality of plate portions arranged in laterally and circumferentiallyspaced relation and centrally connected to said hub, said plate portionsbeing alternately staggered adjacent opposite ends of said hub, eachplate portion having a pair of apertures therein in registry withsimilar apertures in laterally spaced adjacent plate portions, amounting pin received in each pair of registering apertures, said driverollers being rotatably mounted on said pins.

21. The drive of claim 20 wherein said plate portions are of triangularconfiguration and each is apically connected to said hub adjacent thecenter thereof, alternate plate portions being divergently, radiallyangulated from said hub.

References Cited in the file of this patent UNITED STATES PATENTS618,642. Clouser Jan. 31, 1899 1,304,357 Norelius May 20, 1919 1,795,618Ronk Mar. 10, 1931 1,934,627 Norelius Nov. 7, 1933 2,704,942 Koile Mar.29, 1955 FOREIGN PATENTS 276,712 Great Britain Sept. 5, 1927 588,981Great Britain June 9, 1947 577,304 Germany May 29, 1933

